Air respirators used by firefighters and the like which are used with cylinders as air supply sources are conventionally known. Also, there are known high-pressure decompression valves which are used to decompress compressed air under high pressure in cylinders, and supply valves which are used to supply low-pressure air to the wearer of the air respirator by decompressing medium-pressure air obtained through the high-pressure decompression valve into pressure equivalent to atmospheric pressure. The supply valves are also referred to as air supply valves.
One example of the supply valves of this type is disclosed as pilot control two-stage regulator in JP 1983-501656 A (PTL 1). Regarding the regulator used as a scuba pilot regulator, when pressure in the mouth of the user of the air respirator is reduced, variation occurs in the diaphragm, and a linkage arm is moved according to the variation. When the linkage arm is moved, a lever is raised, whereby moving a pin along with the movement of a ball. The movement of the pin allows a pilot valve to open, and the medium-pressure air flows into a control room. A poppet valve is opened by the pressure of the medium-pressure air, and the air decompressed through the poppet valve is supplied to the mouth of the user.